KR101485913B1 - Method for continuous casting of mixed grade - Google Patents

Abstract

The present invention relates to a method of continuously casting hybrid steel which includes steps of: obtaining dimensionless relative concentrations of following steel with respect to preceding steel in real time at a central portion and a surface portion of a strand continuously being casted; calculating a longitudinal position of the strand having the dimensionless relative concentrations of the central portion and the surface portion obtained in real time; comparing each of the obtained dimensionless relative concentrations of the central portion and the surface portion with a reference concentration to predict a mixing portion in the strand; and trimming the predicted mixing portion. According to embodiments of the present invention, dimensionless concentrations at a central portion and a surface portion of a strand are obtained when continuously casting hybrid steel, and a position of a strand having the obtained dimensionless concentrations is calculated to predict the position and length of a mixing portion instead of trimming the mixing portion in a predetermined length regardless of a working condition when continuously casting hybrid steel. Accordingly, accuracy of predicting the position and length of the mixing portion is improved, thereby preventing profit reduction caused by over-trimming the mixing portion, and preventing a poor quality product from being returned to a company due to under-trimming the mixing portion.

Description

[0001] The present invention relates to a continuous casting method of continuous casting,

[0001] The present invention relates to a continuous casting method of a brassiere, and more particularly, to a method of continuous casting different brass types, in which a brass portion of a strand produced by mixing a previous steel type with a subsequent steel type is predicted, To a continuous casting method.

Continuous casting of heterogeneous steels (ie, steels) is a continuous casting operation using molten steel of a new steel type (hereinafter referred to as "subsequent steels") having components different from those of molten steels (hereinafter referred to as "prior steels"). To this end, the molten steel of the subsequent steel species contained in the subsequent ladle is supplied in turn at the end of the operation of the previous steel type. At this time, the molten steel of the previous steel type and the molten steel of the subsequent steel type are mixed in the tundish, and the molten steel is injected into the mold through the submerged entry nozzle.

As a result, a blended portion produced by mixing the gypsum in a certain region of the cast strand is generated, and the blended portion is truncated because it does not satisfy the component specification of the product to be sold, and is mostly reused as scrap iron.

Meanwhile, in order to cut the mixed portion generated by the continuous casting of the bristle type in the related art, the length of the meniscus of the strand has been cut to a certain length based on the position. However, in the case of this cutting method, the position of the mixed portion to be cut is not accurate because it is cut to a certain length based on the meniscus position of the strand regardless of various variables such as the change of the steel type or the casting speed . Therefore, there is a problem that the production rate is lowered excessively compared to the actual mixing portion, or the product is sold as a product in a state where the mixing portion is mixed with the actual mixing portion.

In order to solve this problem, the length of the mixed portion is converted into a table by the type of the previous steel type and the subsequent steel type and combinations thereof, and the length of the mixed portion is converted into a table. The length was cut. However, even in this cutting method, the mixed portion is excessively cut and the region satisfying the design specification is cut and discarded like the mixed portion, or the mixed portion is not cut out, and some of the mixed matters are still present in the product.

In another conventional method, as disclosed in Korean Patent Registration No. 10-0419886, by using operation data such as a ladle weight change amount, a turn weight change amount, a casting speed, and the like of a previously performed operation, And the following steel grades were calculated. The mixed portion was determined by applying the mixed concentration calculated by the hydrodynamic principle, and the mixed portion was cut at both ends of the mixed portion. However, in the case of such a mixed part determining method, the mixing concentration and mixing part are predicted without considering the cross-sectional position of the strand, that is, the surface part and the center part. Therefore, the precise accuracy or reliability of the mixing portion is low, and at least a part of the mixing portion is mixed with the product and is still delivered to the customer.

Korean Patent No. 10-0419886

The present invention provides a continuous casting method of continuous casting of different types of steel, which can automatically cut a mixed portion of strands produced by mixing a previous steel type with a subsequent steel type.

In addition, the present invention provides a continuous casting method capable of calculating the position of a mixed portion of a strand, improving the accuracy of the position and length of a mixed portion, and preventing a product failure due to a mixed portion according to continuous casting.

The present invention relates to a continuous casting method for two or more steels, comprising the steps of: acquiring, in real time, non-dimensional relative concentrations of succeeding steels for previous steels in the inside and on the surface of continuously stranded strands; Calculating a position in a longitudinal direction of a strand having a non-dimensional relative density of an inner surface portion and a surface portion obtained in real time; Comparing the acquired relative intensities of the inner and the outer dimensions with the reference concentration to predict the mixing portion in the strand; And cutting the predicted mixing portion; .

The position of the strand for obtaining the dimensionless relative density is the central portion and the surface portion in the height direction of the strand.

The present invention relates to a continuous casting method of a bimanual type, wherein a relative amount of a previous steel type and a succeeding steel type in a tundish and a relative amount of a subsequent steel type and a subsequent steel type in the mold are used to determine a height Dimensional relative density of a succeeding steel species with respect to a previous steel species at a plurality of positions in a direction of a first direction; Calculating a position in the longitudinal direction of the strand having the dimensionless relative density obtained in real time; Comparing the dimensionless relative concentrations with the reference concentration to predict a mixing part in the strand; And cutting the predicted mixing portion; .

A plurality of positions in the height direction of the strand for obtaining the dimensionless relative density include a central portion and a surface portion of the strand.

Wherein the step of setting the reference concentration comprises the step of setting the reference concentration before the step of acquiring the dimensionless relative concentration of the subsequent steel species for the previous steel species in the continuously cast strand in real time in real time, Setting the lowest concentration among the upper limit concentrations for the respective components of the steel species to the first reference concentration; Setting the highest concentration among the lower limit concentrations for the respective components of the subsequent steel species to a second reference concentration; .

Calculating a component concentration of the previous steel product as a lower limit non-dimensional concentration and an upper non-dimensional concentration in the step of setting the first reference concentration and the second reference concentration; Setting a lowest non-dimensional concentration among the upper non-dimensional concentrations for the respective components of the previous steel type as a first reference concentration; Calculating a component concentration of the subsequent steel product as a lower limit non-dimensional concentration and an upper non-dimensional concentration; And setting the best non-dimensional concentration as the second reference concentration among the lower-limit non-dimensional concentrations for the respective components of the subsequent steel species.

When the lower limit non-dimensional concentration of the previous steel grade is larger than the upper non-dimensional concentration of the previous steel grade in the calculation of the lower limit non-dimensional concentration and the upper non-dimensional concentration in the previous steel grade, Is replaced with the upper limit non-dimensional concentration value of the previous steel grade, and the upper limit non-dimensional concentration value of the previous steel grade is replaced with the lower limit non-dimensional concentration value of the previous steel grade; Dimensional concentration and the upper limit non-dimensional concentration of the subsequent steel species, and when the lower limit non-dimensional concentration of the subsequent steel species is larger than the upper non-dimensional concentration of the subsequent steel species, The non-dimensional concentration value is replaced with the upper non-dimensional concentration value of the subsequent steel grade, and the upper non-dimensional concentration of the subsequent steel grade is replaced with the lower non-dimensional concentration of the subsequent steel grade.

Dimensional non-dimensional relative concentration of at least one of the obtained central portion and the non-dimensional relative concentration of the surface portion is determined to be a mixed state when the non-dimensional relative concentration is out of the reference concentration, The position in the longitudinal direction of the strand having the dimensionless relative density at which the relative concentration deviates from the reference concentration is determined as the mixing portion.

Determining a position in the longitudinal direction of the strand where the non-dimensional relative concentration of the obtained central portion reaches the reference concentration as the starting point of the mixing portion, determining a position in the longitudinal direction of the strand in which the non- Is determined as the end point of the mixing portion.

A process of receiving and storing concentration data of each of the molten steel remaining amount, casting speed, previous steel grade, and subsequent steel grade of the tundishes online before acquiring the dimensionless relative concentration of the subsequent steel grade for the previous steel grade; And detecting a pore signal of the subsequent ladle.

Dimensional relative concentration of each of the central portion and the surface portion of the strand in real time from the point at which the opening signal of the subsequent ladle is detected, counting the non-dimensional concentration acquisition time from the time point of detection of the opening signal of the next ladle, A process of comparing with time in real time; Comparing the dimensionless relative concentration of the obtained center portion with a first reference concentration when the dimensionless concentration acquisition time is less than or equal to a reference time and comparing the dimensionless relative concentration of the obtained surface portion with a second reference concentration; And terminating acquisition of the dimensionless relative concentration of each of the center portion and the surface portion of the strand when the concentration acquisition time exceeds the reference time.

Determining whether the kind between the previous steel grade and the succeeding grade grade is included in the predefined gypsum cut table after finishing acquiring the dimensionless relative concentration of each of the center portion and the surface portion of the strand; If the type of the previous steel type and the succeeding steel type that are currently in operation are included in the pre-set pre-cut table, the process is truncated to the cut length of the pre-selected grade. If the type of the previous steel species currently being operated and the type of subsequent steel species are not included in the pre-determined grit type cut-off table, the process may include truncating to a predetermined cut length.

A step of transmitting a virtual ladle opening signal in the process of detecting the subsequent ladle opening signal; Detecting the weight of the turn-by-turn in real time in milliseconds (ms) from the time when the virtual ladle-opening signal is transmitted; Calculating a weight of the turn-disc detected in units of milliseconds (ms) at an average turn-off weight of a predetermined time interval in seconds; And setting a subsequent ladle opening time through a time point at which the average turn-off weight continuously rises.

When La W _td (t) to the turn-dish glass tangryang weight of the present time, W _td (t- △ t) turn-dish glass tangryang weight of an earlier _{time, W td (t) - W} td (t- △ t) and 2 *? T is determined as the opening time of the subsequent ladders when W _td (t) - W _td (t-2 *? T) dimensional relative density of each of the center portion and the surface portion of the strand from the time point t, and stores the amount of turn-around time and the casting speed from t-4 * Δt.

The process of obtaining the dimensionless relative concentration of the subsequent steel species for the previous steel species at the center portion and the surface portion of the strand includes the steps of calculating an inlet volume flow rate Q _{td - in} of the subsequent steel in the turn _-off time; Calculating a mean non-dimensional relative concentration (C _{td - ave} (t +? T)) of the molten steel during turning at the present time using the inlet volume flow rate (Q _{td - in} ) of the subsequent molten steel in the turn-off time; Tundish molten steel average dimensionless relative concentration of the present time _- by using the _{(C td ave (t + △} t)), non-dimensional relative concentration of the molten steel discharged from the tundish at this time (C _td-out (t + ? T)); The current non-dimensional relative concentration of the molten steel discharged from the tundish point _- using the _{(C td out (t + △} t)), the average dimensionless relative concentration of a molten steel in the mold at the moment (C _md-ave (t + △ t)); ( _{Cmd - ave} (t +? T)) of the present molten steel in the mold and the dimensionless concentration ( _{Cmd - in} (t +? T) of molten steel flowing into the mold at the present time , at this point, the process for calculating the dimensionless relative concentration _{(C md _ out (t +} △ t)) of a strand discharged from the mold; includes.

The inlet volume flow rate Q _{td - in} of the subsequent molten steel in the turn-off time is calculated by the equation (5)

&Quot; (5) "

(W _td (t) is a tundish molten steel shot weight, W _td (t + △ of the earlier time t) is a tundish molten steel total weight of this time, Q _{td - out} the molten steel volumetric flow rate discharged from the tundish, ρ _L is the density of the liquid molten steel)

(C _{td - ave} (t +? T)) at the present time is calculated by the equation (6)

&Quot; (6) "

(C _{td _ ave} (t) is the average dimensionless relative concentration of the tundish the molten steel in the earlier time, Q _{td - in} (t) is the inlet volume flow rate of the molten steel flowing into the tundish at an earlier time, C _{td - in} ( t) is the inlet concentration of the follow-up molten steel tundish of an earlier time (dimensionless relative concentration), Q _{td - out} (t) is the molten steel volumetric flow rate discharged from the tundish of an earlier time, C _{td - out} (t) is the previous The molten steel concentration (non-dimensional relative concentration) discharged from the turn-around of the time point, and ρ _L is the density of the molten steel in liquid phase)

The molten steel concentration (C _{td - out} (t +? T)) discharged from the tundish at the present time is calculated by the equation (7);

&Quot; (7) "

(f _td is the turn-dish within extrapolation _{coefficient, C td _ ave (t +} △ t) is the average dimensionless relative concentration of a molten steel in the tundish at this _{point, C td - in (t +} △ t) is in the tundish at the present time Dimensionless relative concentration of molten steel entering)

At this point in time, the average molten steel concentration in the mold (C _{md - ave} (t +? T)) is calculated by Equation (8)

&Quot; (8) "

(W _md (t) is a molten steel in the mold shot at an earlier time, weight, C _{md - ave} (t) is the average dimensionless relative concentration of a molten steel in the mold at an earlier time, Q _{md - in} (t) is the mold in the previous point, inlet volumetric flow rate of the molten steel, C _{md - in} (t) is the inlet concentration of a molten steel in the mold at an earlier time (dimensionless relative _{concentration), W md (t + △} t) is a molten steel in a total weight of the mold at this time, Q _{md - out} (t) is the volumetric flow rate of molten steel discharged from the mold, C _{md - out} (t) is the dimensionless relative density of the strand discharged from the mold at the previous point of time, and ρ _L is the density of the molten steel)

Density of the strand is discharged from the mold at the present time _{(md _} C _out (t + △ t)) is calculated by the equation (9).

&Quot; (9) "

(f _md is molded within the extrapolation _{coefficient, C md _ ave (t +} △ t) is the average dimensionless relative concentration, C _md of a molten steel in the mold at this time _- that is introduced into the mold at the present time _in (t + △ t) steel Dimensional non-dimensional relative concentration)

In the process of calculating the dimensionless relative density of the strand center portion, 4? 2 is applied to the internal extrapolation coefficient (f _td ) of Equation (7) and 0.7? 2 is applied to the internal extrapolation coefficient (f _md ) 0.4 is used to calculate the dimensionless concentration (C _{md - out - center} ) at the center of the strand.

In calculating the dimensionless relative density of the surface portion of the strand, the internal extrapolation coefficient (f _td ) of Equation (7) is 2.2 ± 0.6 and the internal extrapolation coefficient (f _md ) of Equation (C _{md - out - surface} ) of the surface of the strand.

The use of liquid phase density to the molten steel density (ρ _L) values in equation 5, 6, 8, respectively, and apply the 7000 to 7400 kg / m ³ density values in the molten steel.

Setting a position of the strand at which acquisition of dimensionless relative concentration of the strand surface portion starts; And setting a position of the strand at which acquisition of dimensionless relative concentration of the strand center portion is started,

Setting a strand position at the subsequent ladle opening point to a position at which acquiring a dimensionless relative concentration of the strand surface portion starts, and setting a position of -4 4 m at the strand position at the subsequent ladle opening point to a dimensionless relative Set to the position where concentration acquisition starts.

(A _md ) of the cross section of the strand divided by the solid-phase density (ρ _s ) of the molten steel in the process of calculating the longitudinal position of the strand having the dimensionless relative density of the obtained surface portion, Is calculated by the equation (10) for dividing the discharged molten steel volume flow rate (Q _{md - out} ).

&Quot; (10) "

(Q _{md _ out} is the volume flow rate of the molten steel discharged from the mold, A _md is the cross-sectional area of the strand, and ρ _s is the solid-phase molten steel density of 7600 to 8000 kg / m ³ )

In the process of calculating the longitudinal position of the strand having the non-dimensional relative concentration of the obtained center portion, a position of -4 ± 4 m at a position having a non-dimensional relative concentration of the obtained surface portion is calculated as a non- Set the position of the branch.

Dimensional non-dimensional relative concentration of the strand surface portion obtained in real time from the point of the strand where the non-dimensional relative concentration of the strand center portion obtained in the real time reaches the first reference concentration is mixed to the point of the strand where the non- Forewarned.

Setting a position of the strand at which the dimensionless concentration of the strand center obtained in the real time reaches the first reference concentration to the first cutout position; Setting a position of the strand in which the dimensionless concentration of the strand surface portion obtained in real time reaches the second reference concentration to a second cut position of the strand; And performing trimming at each of the first cut position and the second cut position to cut the mixed portion.

The process of predicting the mixed portion of the strand and the process of cutting the predicted mixed portion are performed in an online process.

According to embodiments of the present invention, the dimensionless concentration of each of the center portion and the surface portion of the strand is obtained, and the length and position of the mixing portion are derived using the dimensionless concentration. That is, as in the prior art, the non-dimensional concentration of each of the center portion and the surface portion of the strand is obtained every time the fishing line is run, and the strand position having the obtained non-dimensional concentration is set, The position and length of the mixing section are predicted. Accordingly, as the accuracy of the position and length of the mixing portion is improved, the profitability of the mixing portion can be prevented from being reduced due to over-cutting, and the problem of shipping the defective product due to undercutting of the mixing portion to the customer can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
2 is a view showing a main part of a general continuous casting facility for explaining a process of producing a strand or a cast steel through a supply and solidification process of molten steel
FIG. 3 is a flowchart illustrating a method of predicting a mixed-portion blending portion of a strand and a method of cutting a mixed portion using the same according to an embodiment of the present invention.
FIGS. 4 and 5 are flow charts illustrating a method of cutting a mixed portion in a continuous casting method according to an embodiment of the present invention
6 is a flowchart illustrating a process of detecting a subsequent ladle opening signal according to an embodiment of the present invention.
7 is a flowchart illustrating a method for setting a first reference concentration and a second reference concentration for predicting a gaseous mixture portion of a strand by a method according to an embodiment of the present invention.
FIG. 8 is a graph showing the dimensionless concentration of the components of the previous steel species and the subsequent steel species, obtained by the method according to the embodiment of the present invention
9 is a graph showing the non-dimensional concentration distribution of Cr in the vertical direction (cross-sectional thickness) and the casting direction (longitudinal direction)
10 is a photograph showing the change in concentration in the mold with time during the continuous casting operation
Fig. 11 is a graph showing the results of concentration distribution calculation for the longitudinal direction and the cross section of the strand after final solidification, taking into consideration only the influence of the mold, without considering the influence of the turn-
12 is a flow chart illustrating a method for obtaining a strand center portion and a surface portion non-dimensional concentration according to an embodiment of the present invention
FIG. 13 is a graph showing a comparison between data obtained by non-dimensional concentration of the central portion and the surface portion of the strand in the method according to the embodiment of the present invention and results obtained by measuring the actual component in the longitudinal direction with respect to the cast strand
FIG. 14 is a graph showing a comparison result of data obtained by predicting a mixing part according to an embodiment of the present invention,
FIG. 15 is a graph showing an analysis result of a length of a mixing portion for one year through a mixing portion prediction method according to an embodiment of the present invention

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be understood, however, that the invention is not limited to the disclosed embodiments, but is capable of other various forms of implementation, and that these embodiments are provided so that this disclosure will be thorough and complete, It is provided to let you know completely.

Hereinafter, the solidified material which is solidified in the mold and drawn out or discharged to the outside of the mold and is extended in the casting direction is referred to as a 'strand', and a strand cut to a predetermined length is referred to as a 'slab' .

1 is a view showing a general continuous casting facility. FIG. 2 is a view showing a main part of a general continuous casting facility for explaining a process of producing a strand or a cast steel by supplying and solidifying molten steel.

1 and 2, a continuous casting installation includes refined molten steel and includes a movable ladle 100 (110; 120), a tundish 200 (not shown) for receiving molten steel supplied from the ladle 100 A mold 300 having one end connected to the turn-dish 200 and at least a part of the lower end being inserted into the mold 300; A plurality of rollers 500 for conveying the strand S drawn from the mold 300 in the casting direction, a plurality of rollers 500 A plurality of segments 600 for injecting cooling water into the strand S being conveyed by the mold 300 and a strand S continuously produced from the mold 300 are cut into a predetermined size to produce a cast 700 having a predetermined shape (Not shown). Here, the cutter 800 may be a gas torch or a hydraulic shearing machine or the like.

The turn-dish 200 has a discharge port for supplying molten steel to the mold 300, and a plurality of discharge ports may be provided according to the continuous casting facility, and the number of the molds 300 corresponding to the number of the discharge ports is provided. Therefore, in the case of a continuous casting equipment having a plurality of molds 300, a plurality of strands S are solidified and drawn out from the mold 300.

In the continuous casting of two or more types of steel, molten steel of different component steel is accommodated in the first ladle 110 and the second ladle 120, and either one of the ladles 110 or 120 supplies molten steel to the turn- Upon completion, the ladle turret (not shown) rotates 180 degrees so as to be able to alternate with the other ladle 110 or 120. As a result, different types of molten steel can be alternately supplied in turn. For example, the molten steel stored in the first ladle 110 is supplied to the turn-dish 200 to perform casting, and the molten steel of the second ladle 120 is supplied to the turn-dish 200 at the end of casting and cast , And continuously casting the gypsum.

In the continuous casting of this type of steel, the molten steel (hereinafter, referred to as the previous steel grade) and the molten steel (hereinafter referred to as the succeeding steel grade) of the steel grade to be injected subsequently are cast in the turn-dish 200 and the mold 300 A mixed portion is formed in which the old steel species and the subsequent steel species are mixed and solidified in the strand (S).

Therefore, in the present invention, in the continuous casting step, the concentration of the strand (S) is obtained in real time by an online system, the position of the strand (S) having the obtained concentration is calculated, The present invention provides a continuous casting method of this kind capable of improving the accuracy of mixing part prediction and automatically cutting the mixing part by predicting the position in real time.

FIG. 3 is a flowchart sequentially illustrating a method of predicting a mixed portion of a strand and a method of cutting a mixed portion using the same according to an embodiment of the present invention. FIGS. 4 and 5 are flowcharts of a method of cutting a mixed portion in a continuous casting method according to an embodiment of the present invention, and include a mixing portion prediction method and a mixing portion trimming method in FIG.

Hereinafter, with reference to FIGS. 3 to 5, a method of cutting a mixed portion of a strand at the time of continuous casting of a brassiere according to an embodiment of the present invention will be described. At this time, in the continuous casting equipment having a plurality of strands which are solidified and drawn out from a plurality of molds, each strand is supplied with a uniform flow of molten steel by a flow control device inside the turn-dish, for example, a dam or a weir The method of cutting the mixed portion in each strand is applied in the same manner. Therefore, only the case of applying one strand will be described.

Referring to FIG. 3, the method for predicting a mixed-portion of strand blanks according to an embodiment of the present invention includes a step S100 of storing process variables or process data for continuous casting of blanks, a ladle containing a subsequent steel grade (S300) of setting a first reference concentration and a second reference concentration for predicting a gaseous mixture portion of the strand to be solidified and drawn out from the mold, (S400) of obtaining the non-dimensional relative concentration of the succeeding steel species with respect to the steel species in real time and calculating the position in the longitudinal direction of the strand having the inner and the surface non-dimensional relative concentration calculated in real time (S400) Dimensional relative concentration and the first reference concentration in real time, and comparing the obtained relative non-dimensional relative concentration of the strand surface with the second reference concentration in real time (S600), a process of predicting the mixed portion in the strand (S700) according to the result of comparison between the non-dimensional relative concentration of each of the obtained inner and surface portions and the first and second reference concentrations, (S1100).

Here, the inside and the surface portion of the strand are the inside and the surface in the longitudinal direction (that is, the left and right direction) of the strand or the up and down direction (or the height direction) of the strand intersecting the casting direction, And the surface portion may be any one of an upper surface and a lower surface of the strand.

In other words, the dimensionless relative density of the succeeding steel species for the previous steel species is, in other words, the degree or amount of the subsequent steel species mixed with respect to the previous steel species, '.

The non-dimensional concentration is a concentration represented by a value of 0 or more and 1 or less, representing a general concentration value in a dimensionless ratio or dimensionless. Therefore, the dimensionless relative density of the succeeding steel species with respect to the previous steel species can be expressed as a value of 0 or more and 1 or less. The dimensionless concentration of the previous steel species is set to 0, and the dimensionless concentration of the subsequent steel species is defined to be 1. For example, when the dimensionless relative density is 1, it means that the subsequent steel species in the molten steel or the strand is 0%, that is, there is no introduction of the subsequent steel species. On the contrary, when the dimensionless relative concentration is 1, the following steel species in the molten steel or in the strand are 100%. For example, if the dimensionless relative density is 0.4, it means that 60% of the previous steel grade and 40% of the succeeding grade grade are mixed in the molten steel or strand.

The first reference concentration and the second reference concentration, which are compared with the dimensionless relative concentration of each of the central portion and the surface portion of the strand obtained in real time, are the dimensionless concentration values.

The method of predicting and trimming the gypsum mixed portion according to the embodiment shown in FIG. 3 is a method of predicting the gypsum mixed portion as shown in FIG. 3 according to the dimensionless relative concentration acquisition time of each of the central portion and the surface portion of the strand, And the trimming method may or may not be employed.

In other words, when the concentration acquisition time for acquiring the dimensionless relative concentration of each of the center portion and the surface portion of the strand is equal to or shorter than the reference time, the non-dimensional concentration of each of the obtained central portion and the surface portion is compared with the first and second reference concentrations And proceeds to a subsequent step of predicting the mixing portion. Conversely, when the concentration acquisition elapsed time of the central portion and the surface portion of the strand has passed the reference time, the concentration acquiring step of each of the center portion and the surface portion is ended. The mixed portion is cut according to the data table in which the predetermined length of the mixed portion is cut according to the previous steel type and the subsequent steel type, or cut to a predetermined length irrespective of the type between the previous steel type and the subsequent steel type.

FIGS. 4 and 5 illustrate a method of automatically predicting the position of the mixing portion according to the dimensionless relative concentration acquisition time of each of the strand center portion and the surface portion described above, or cutting the mixed portion using the predetermined cut length data table according to the combination , And a series of steps of truncating to a predetermined constant length.

Referring to FIGS. 4 and 5, the continuous casting method of the present invention according to an embodiment of the present invention includes a step S100 of storing process data in accordance with continuous casting of continuous casting, a step S200 of detecting the openings of subsequent rails, (S300) of setting a first reference concentration and a second reference concentration for prediction of a gaseous mixture portion of a strand which is solidified and drawn out from a mold, obtaining a non-dimensional relative concentration of each of the central portion and the surface portion of the strand in real time, (S400) of calculating a strand position having a non-dimensional relative concentration of each of the central portion and the surface portion obtained at the time point (S400), and comparing the non-dimensional relative concentration acquisition time of the central portion and the surface portion of the strand with a reference time do.

In step S300, a first reference concentration and a second reference concentration for predicting the gaseous mixture portion of the strand that is solidified and drawn out from the mold are set after the process of detecting the opening signal of the subsequent ladle in operation S200. However, The procedure of detecting the opening signal of the subsequent ladle (S200) and the process of setting the first reference concentration and the second reference concentration for the prediction of the gaseous mixture portion of the strand which is solidified and drawn out from the mold may be reversed.

Then, when the acquisition time of the center portion of the strand and the non-dimensional relative concentration of the surface portion are equal to or less than the reference time (yes), the obtained strand center non-dimensional relative concentration is compared with the first reference concentration, A step S600 of comparing the reference concentration in real time (S600), a step of predicting and determining the position of the mixed portion of the strand according to the comparison result between the obtained relative concentration of the central portion and the surface portion and the first and second reference concentrations (S700) And cutting the predicted mixture portion (S1100).

In the case where the non-dimensional relative concentration acquisition time of the center portion and the surface portion of the strand exceeds the reference time (NO), a process of ending acquisition of the non-dimensional relative concentration of each of the central portion and the surface portion of the strand (S800) (S900) of determining whether the previous steel type and the succeeding steel type are included in the preset mixed length cut length table (S900). If it is determined that the combination of the previous steel type and the succeeding steel type is not included in the predetermined cut length table (S1200), a combination of a previous steel type and a succeeding steel type in operation is searched in the mixed subdecision length table and a corresponding length is searched (S1200) (NO), a step S1300 of trimming a predetermined fixed length, for example, a maximum length, is performed.

Hereinafter, each step of the continuous casting method according to the embodiment of the present invention will be described in detail with reference to FIGS. 6 to 14. FIG.

FIG. 6 is a flowchart specifically illustrating a process of detecting a subsequent ladle opening signal according to an embodiment of the present invention. 7 is a flowchart illustrating a method for setting a first reference concentration and a second reference concentration for predicting a gaseous mixture portion of a strand by a method according to an embodiment of the present invention. 8 is a graph showing the dimensionless concentration of the components of the previous steel type and the subsequent steel type obtained by the method according to the embodiment of the present invention. 9 is a graph showing the non-dimensional concentration distribution of Cr in the vertical direction (cross-sectional thickness) and the casting direction (longitudinal direction) of the cast steel produced by the continuous casting. 10 is a photograph showing the change in the concentration in the mold with the lapse of time at the time of continuous briquette casting. 11 is a result of calculation of the concentration distribution in the longitudinal direction and the cross section of the strand after the final solidification, taking into account only the influence of the mold, without considering the influence of the tundish at the time of continuous briquette casting. 12 is a flowchart showing a method of obtaining the strand center portion and surface portion density according to an embodiment of the present invention. 13 is a graph comparing the data obtained by measuring the concentration of the center portion and the surface portion of the strand by the method according to the embodiment of the present invention and the result of measuring the actual component in the longitudinal direction with respect to the cast strand. FIG. 14 is a graph comparing data obtained by predicting a mixing portion according to an exemplary embodiment of the present invention and measuring the concentration by taking a predicted mixing portion.

In step S100 of storing the briquette continuous casting process data, information such as the casting condition, the composition of the briquette, and the like, which is variable data for the prediction of the strand mixing portion, is stored. That is, the amount of molten steel remaining in the tundish, the casting speed, the concentration of the molten steel (hereinafter referred to as the previous steel grade) and the concentration of the molten steel (hereinafter referred to as the succeeding steel grade) do. It is desirable that such process data storage is initialized and newly set and stored each time the boiler is operated. In addition, when multiple strands are drawn from a continuous casting facility, the casting speed for each strand is stored.

In the embodiment of the present invention, the dimensionless relative concentration of the strand is obtained from the subsequent ladle opening time. Therefore, it is necessary to accurately detect the signal that the ladle storing the subsequent steel species is opened. Referring to FIG. 6, in step S200, a pseudo open signal of a subsequent ladle is transmitted (step S210). In step S210, a pseudo open signal of a subsequent ladle is transmitted in real time (S230) of calculating a turn-off weight detected in units of milliseconds (ms) by an average turn-off weight of a second interval, (Step S240) of determining whether or not the average turn-off weight calculated in accordance with the elapse of time is continuously increased by receiving the average turn-around weight data in real time, (Step S250).

On the other hand, conventionally, when detecting the subsequent ladle opening signal, when the slide gate of the next ladle is opened beyond a predetermined opening rate, for example, 100%, the signal is received and detected as a subsequent ladle opening signal. However, even if the slide gate is opened, the discharge port of the succeeding ladle is clogged and the molten steel is often not discharged. Even if molten steel is not discharged from the ladle, the operation of only the slide gate is sensed and the subsequent ladle open signal is detected.

Therefore, in order to solve this problem in the past, in order to detect the subsequent ladle opening signal for mixing prediction, it is measured with time using a sensor for sensing the weight of the tundish, And measured at short time intervals. Then, the weight change value of the turn-measure measured in real time at the intervals of milliseconds (ms) is analyzed. When the turn-off weight continuously increases, the PLC (Programmable Logic System) . However, the tundish weight value measured in very short intervals in milliseconds (ms) is hunting due to the sensitivity of the sensor. Accordingly, in the PLC (Programmable Logic System), even when the subsequent paddles are not actually opened, the padding signals of the subsequent paddles are frequently transmitted. In order to solve this problem, the PLC (Programmable Logic System) transmits the open-loop signals of the subsequent ladle to the time when the turn-off weight of the continuous rise time is re-detected after the turn-on weight increases continuously. However, when the tundish weight at the time of the continuous rise is re-detected, the ladle opening signal is frequently delayed, unlike the actual case. In order to solve the problem of the delay of the open signal, the data of 10 minutes before the time when the turn-off weight at the last rising time is re-detected and the time at which the turn-delay weight is lowest are set as the subsequent ladle opening signal Was performed again. However, this method is a post-correcting method, and there is a problem that it is not possible to detect the open signals of the subsequent laths in real time. Therefore, the delay signal of the next lag is still delayed, or an inaccurate problem arises, which is a factor for reducing the mixing part prediction accuracy.

Therefore, in the present invention, in order to accurately detect the opening signal of the succeeding ladle, the casting speed and the remaining amount of molten steel are lowered in accordance with the bifurcated operating conditions, and when the casting speed and the turn- , The virtual pager signal of the subsequent ladle is transmitted from the PLC (Programmable Logic System) (S210). Then, the turn-off weight is measured in units of milliseconds (ms), for example, in units of 200 ms from the point at which the virtual pager signal of the subsequent ladle is transmitted (S220). Subsequently, an average turn-off weight is calculated (S230) at a predetermined interval of a turn-measure weight detected in milliseconds (ms) in units of seconds (e.g., 1 second or 2 seconds) (S230) The weight is analyzed in real time, and it is determined whether the weight is continuously increased (S240). That is, when described as a formula, 'W _td' to the turn-dish glass tangryang weight, of the time 't' this point, when the t- △ t is time of the earlier _{time, W td (t) - W} td (t- 2 *? T is determined to be the opening time of the subsequent ladders when both W _td (t) and W _td (t-2 *? T) are equal to or greater than '0' And transmits an open signal. Then, the non-dimensional relative concentration of each of the center portion and the surface portion of the strand is calculated from the time point of t-2 * Δt. To do this, the amount of turn-off time and the casting speed are stored from t-4 * Δt, Make sure the wealth is predictable.

The first and second reference concentrations, which are compared with the non-dimensional relative concentration and the surface non-dimensional relative concentration at the center of the strand for the purpose of blending of the gypsum, are non-dimensional concentration values. Hereinafter, a method of calculating the first and second reference densities according to the embodiment of the present invention will be described with reference to FIG.

Referring to FIG. 7, a method of setting a first reference concentration and a second reference concentration for predicting a mixed portion of a strand according to an embodiment of the present invention includes receiving concentration data of all components of a previous steel species and a succeeding steel species (S310a, S310b), the lower limit non-dimensional concentration and the upper limit non-dimensional concentration for each component of the previous steel grade are calculated (S320a), and the lower limit non-dimensional concentration and the upper non- (S330a), the lowest non-dimensional concentration value among the upper non-dimensional concentration values for the respective components of the previous steel species is set as the first reference concentration (S330a), and the lower limit for each component of the subsequent steel species And setting the best non-dimensional concentration among the dimensional concentration values to the second reference concentration (S330b).

That is, the lower limit non-dimensional concentration for each component of the previous steel grade is calculated by Equation (1), and the upper limit non-dimensional concentration for each component of the previous steel grade is calculated by Equation (2). Further, the lower limit non-dimensional concentration for each component of the steel type is calculated by Equation (3), and the upper limit non-dimensional concentration for each component of the steel type is calculated by Equation (4).

In the above-mentioned expressions (1) to (4), when the lower limit non-dimensional concentration of the previous steel grade is larger than the upper non-dimensional concentration of the previous steel grade in calculation of the dimensionless concentration for each component concentration, The upper non-dimensional concentration value of the previous steel species is replaced with the lower non-dimensional concentration value of the previous steel species. In addition, when the lower limit non-dimensional concentration of the succeeding grade is larger than the upper limit non-dimensional concentration of the subsequent grade, the lower limit non-dimensional concentration value of the subsequent grade is the upper limit non-dimensional concentration value of the subsequent grade, The concentration value is replaced by the lower limit non-dimensional concentration value of the subsequent steel grade. This is applied when the component concentration of the previous steel grade is higher than that of the subsequent steel grade.

For example, if the C concentration of the previous steel grade is 0.4 wt% (0.38-0.42 wt%), and then the C concentration of the steel grade is 0.2 wt% (0.18-0.22 wt%), The C dimensionless concentration of the previous steel species is 0 (0.1 ~ - 0.1). That is, the upper non-dimensional concentration of the previous steel grade becomes -0.1, and the lower non-dimensional concentration of the previous steel grade becomes 0.1, thereby changing this.

On the other hand, according to the type of the steel to be produced, there is a design specification concentration for each component. That is, if the concentration for each component is included in the design standard concentration range, it satisfies the steel grade condition to be manufactured. The design standard concentration range includes the lowest value and the best value for each component, and the value between the lowest value and the highest value . Therefore, even in the continuous casting of the bridges, there is a design standard concentration range for each component of the previous steel type, and there is a design standard concentration range for each component of the subsequent steel type.

The concentration of each component of the previous steel species is the concentration of each component of the molten steel that is cast in the current operation of the steel gantry. This is the concentration determined through the refining process before the molten steel is supplied by turning, It is the concentration value included in the design specification concentration range of steel grade. Likewise, the concentration for each component of the succeeding grade is the concentration of each component of the molten steel to be subsequently fed, also the concentration determined through the refining process before being fed into the tundish, Concentration value.

In the above equations (1) to (4), the lower limit concentration of the previous steel design specification, the upper limit concentration of the previous steel design specification, the lower limit concentration of the subsequent steel design specification, the upper limit concentration of the subsequent steel design specification, To calculate the lower and upper non-dimensional concentrations of the previous steel species, and the lower and upper non-dimensional concentrations of the subsequent steel species. Among the non-dimensional upper limit concentration values for the respective components of the previous steel type, the non-dimensional concentration value of the lowest level is set as the first reference concentration, and among the lower limit non-dimensional concentration values for each component of the subsequent steel type, The non-dimensional concentration value is set to the second reference concentration. In the following process, the first reference concentration is a value which is compared with the center non-dimensional relative concentration of the strand calculated in real time, and the second reference concentration is a value which is compared with the surface non-dimensional relative concentration of the strand calculated in real time .

FIG. 8 is a graph showing dimensionless concentrations of the components of the prior steel and the subsequent steel, calculated by the method according to the embodiment of the present invention. For example, C, Mn, and Cr are included in each of the previous and subsequent steel types, and the lower limitless dimension of the C, Mn, and Cr components of the previous steel type and the subsequent steel type, respectively, The concentration and the upper limit non-dimensional concentration are shown in FIG. 8, the upper limit non-dimensional concentration of Cr is smaller than the upper limit non-dimensional concentration of C, Mn among the upper limit non-dimensional concentrations of C, Mn, and Cr. Thus, the upper limit non-dimensional concentration of Cr is set to the first reference concentration. The lower limit non-dimensional concentration of Cr is larger than the upper limit non-dimensional concentration of C and Mn among the lower limit non-dimensional concentrations of C, Mn and Cr, respectively. Thus, the lower limit non-dimensional concentration of Cr is set to the second reference concentration. Therefore, according to the example of Fig. 8, the first reference concentration, which is the lowest limit of the non-dimensional concentration for predicting the mixing portion, is 0.07, and the second reference concentration, which is the uppermost limit, is 0.95. In other words, the dimensionless concentration of the mixed portion is 0.07 or more to 0.95 or less, and the region from the point where the centerless dimensionless relative concentration of the center of the strand calculated in real time is 0.07 to the point where the surface non-dimensional relative density is 0.95 is predicted as the mixing portion .

As described above, the non-dimensional concentration of the lowest non-dimensional concentration among the highest non-dimensional concentrations of each component of the previous steel is compared with the non-dimensional relative concentration of the central portion calculated in real time as the first reference concentration, The reason why the non-dimensional concentration of the highest one of the non-dimensional concentrations is compared with the non-dimensional relative concentration of the surface portion calculated in real time as the second reference concentration will be described below.

During the continuous casting of the bridges, the concentration of one end of the mixed portion of the strand mixed with the previous steel and the succeeding steel is satisfied with the design standard concentration of the previous steel, and the other end of the mixed portion satisfies the design standard concentration of the subsequent steel. The area between one end and the other end of the mixing section is outside the design standard concentration range of the previous and subsequent steel species.

Referring to Fig. 9, it can be seen that the concentration varies depending on the vertical direction of the cast steel (in the direction of the thickness of the end face) and the casting direction (the longitudinal direction). The vertical and horizontal positions of the strand, that is, the non-dimensional relative concentration of the central portion and the surface portion, show patterns of different tendencies. More specifically, the blending between the previous steel species and the subsequent steel species appears on the surface portion of the strand after the opening time of the subsequent ladle. However, in the case of the center portion, mixing occurs from the strand position before the opening time of the next ladle. This is because the mixed and remelted molten steel produced through the tundish and the mold is diffused to the center of the non-solidified molten steel layer in the strand. That is, the center portion of the strand starts to be mixed with the previous steel species and the subsequent steel species from the previous point in comparison with the surface portion.

Accordingly, in the present invention, when the non-dimensional relative density of the center portion in the strand obtained in real time reaches the lowest non-dimensional density value (i.e., the first reference density) among the upper non-dimensional density values for each component of the previous steel species Or the lowest non-dimensional concentration value (that is, the first reference concentration), the mixing start state is determined, and the position in the longitudinal direction of the strand is determined as the first cut position. When the dimensionless relative density of the surface portion in the strand produced in real time reaches the highest non-dimensional concentration value (i.e., the second reference concentration) among the lower limit non-dimensional concentration values for each component of the subsequent steel species, When the non-dimensional concentration value (that is, the second reference concentration) is exceeded, it is judged as the mixing end state, and the strand position is determined as the second cut position. To be more specific, among the upper non-dimensional concentration values for the respective components of the previous steel species, the dimensionless relative concentration of the center portion is the position of the strand in the longitudinal direction having the lowest non-dimensional concentration as the starting position of the mixing portion, Among the lower limit non-dimensional concentration values for each component of the subsequent steel grade, the longitudinal position of the strand having the highest non-dimensional concentration is the end position of the mixing portion. Therefore, in the present invention, the lowest non-dimensional concentration among the upper non-dimensional concentration values for each component of the previous steel type is referred to as a first reference concentration, and the first reference concentration is compared with the non-dimensional relative concentration of the obtained central portion . Then, among the lower limit non-dimensional concentration values for each component of the subsequent steel species, the highest non-dimensional concentration is named as the second reference concentration, and the second reference concentration is compared with the obtained surface non-dimensional relative concentration, Mixed mixing is forethought. That is, the longitudinal position of the strand in which the non-dimensional relative concentration of the center portion obtained in real time reaches the first reference concentration is defined as the first cut position, and the length of the strand in which the dimensionless relative concentration of the surface portion reaches the second reference concentration And the mixing position is cut by setting the direction position to the second cut position.

On the other hand, conventionally, in the case of predicting the mixing portion, the mixing portion is predicted without regard to the position of the cross-section of the strand, that is, the surface portion and the center portion. That is, conventionally, at a position in the lengthwise direction of the strand, the concentration of the strand is regarded as being equal to the concentration of the center portion and the surface portion. Therefore, the accuracy of prediction of the position of the mixing portion or the mixing portion is low, and the mixing portion is frequently mixed with the product and delivered to the customer.

Therefore, in the present invention, it is recognized that the center portion and the surface portion concentration are different at one position in the strand lengthwise direction, and the non-dimensional relative density of each of the center portion and the surface portion in the strand is separately obtained, Foresight.

In a typical continuous casting operation of a brassiere, when a subsequent steel grade is fed into the turndish, the former steel grade and the succeeding steel grade are mixed in the tundish. In this process, some mixed steel grades are discharged during the mixing of the previous steel grade and the subsequent steel grade, Are continuously remixed while recirculating the interior of the turn dish. The molten steel mixed and re-mixed in the tundish is discharged to the mold through the immersion nozzle. The molten steel discharged through the immersion nozzle has a turbulent flow. Therefore, the mixed molten steel flowing into the mold from the tundish makes a recirculating flow in the upper region by the molten steel turbulent flow in the mold, so that the mixing and re-mixing phenomenon is repeatedly generated in the mold, (See Fig. 10). 11, when a strand having been solidified from the mold has a mixed portion in which a previous steel type and a succeeding steel type are mixed, and only mold mixing is considered without considering the tundish mixing, when the cast steel has a thickness of 0.4 m, The length of the part is about 4m.

As described above, from the description of Figs. 10 and 11, it can be seen that not only the turn-by-turn but also the blending of the gypsum is carried out in the mold, and the blend containing the former steel species and the succeeding steel species is expressed in the strand by mixing in the mold .

Conventionally, considering only the mixing in the tundish, and considering the mixing part in the mold, the position of the mixing part or the accuracy of prediction of the mixing part is low and at least a part of the mixing part is mixed with the product and transferred to the customer Occurred frequently.

Therefore, in the present invention, not only the turn-over time but also the blending part can be precisely truncated in consideration of biaxial mixing in the mold, thereby improving the accuracy of trimming of the mixed part.

(S400) of calculating the longitudinal position of the strand having the dimensionless relative concentration and the dimensionless relative concentration of the center portion and the surface portion of the strand at the time of continuous casting of the two or more grades, Dimensional relative density of each of the center portion and the surface portion of the center portion and the surface portion of the center portion and the surface portion, and calculating a position of the strand having the calculated central portion and surface portion density (S420).

In order to calculate the concentration (S410) of the central portion and the surface portion of the strand in real time from the detection of the subsequent ladle opening signal, the present invention calculates the center portion and the surface portion concentration of the strand in consideration of mixing in the mold as described above (Hereinafter referred to as " Equation 9 ") includes the concentration of the steel species discharged from the mold. 'T + Δt' expressed in the following equation means the current point, and 't' means the previous point.

Hereinafter, the process of acquiring the concentration of the center portion and the surface portion of the strand in real time from the detection point of the subsequent ladle opening signal will be described. In the embodiment of the present invention, the concentration of the central portion and the surface portion of the strand is calculated or calculated by the following mathematical expressions. In other words, 'concentration acquisition of the central part and surface part of the strand' can be expressed as 'concentration calculation of the central part and surface part of the strand'.

From the physical viewpoint, the amount of change in the molten steel inflow into the tundish can be expressed as the value obtained by dividing the weight change amount of the tundish by the time variation (t) and the density of the molten steel. In the embodiment of the present invention, first, the flow volume Q _{td - in} of the subsequent molten steel in the turn-off time is calculated using the above-described physical concept of the molten steel inflow change amount in the turn-off time (S411).

At this time, the inlet volume flow rate Q _{td - in} of the subsequent molten steel in the turn-off time can be calculated by the following equation (5).

W _td (t) is a tundish molten steel shot weight, W _td from the previous time point (t + △ t) is a tundish molten steel total weight of this time, Q _{td -} steel volume flow rate _out is discharged from the tundish, ρ _L Is the density of the liquid molten steel.

The total gross weight W _td (t) of the _tinned steel at the previous time point and the total gross weight W _td (t +? T) of the _tinned steel at the present time are measured in real time from the sensor provided at the outer lower part of the turn- The molten steel volume flow rate (Q _{td - out} ) discharged from the tundish is calculated as the sum of the casting speed measured from the sensor provided at one side of the strand and the mold cross-sectional size product. In addition, since the molten steel has a liquid phase, the molten steel density of 7000 kg / m ³ to 7400 kg / m ³ is applied instead of the solid molten steel density of 7600 kg / m ³ to 8000 kg / m ³ . More specifically, for example, when described, instead of the molten steel density of about 7800kg / m ³ in the solid phase, and applying the liquid molten steel density of about 7200kg / m ^3.

Calculates a _{- (ave (t + △ t} ) C td) (S412) - Then, the yield of the tundish in the subsequent molten steel inlet volumetric flow rate of the average dimensionless relative concentration of the tundish the molten steel by using the (Q _{td in)} . The molten steel flow generated in the tundish can be classified into a secondary flow including a primary flow and a dead zone, and accordingly, the concentration of molten steel according to the position of the molten steel in the turn- Can be locally different. However, in the present invention, it is assumed that the average non-dimensional relative concentration of the molten steel in the tundish is represented by a certain value without considering the local flow for the purpose of predicting the concentration occurring depending on the upper, lower, left, and right positions of the strand And this is defined as the average dimensionless relative density of the molten steel in the turn-on die. At this time, the molten steel mean non-dimensional relative concentration (C _{td - ave} (t +? T)) in the tundish can be calculated by the following equation (6).

_{C td - ave (t + △} t) is the average dimensionless relative concentration of the tundish the molten steel at the moment, W _td (t) is a tundish molten steel shot weight at an earlier time, C _{td _ ave} (t) is a point before the turn-dish average dimensionless relative concentration of the molten steel, Q _{td - in} (t) is the inlet volume flow rate of the molten steel flowing into the tundish at an earlier time, C _{td - in} (t) will follow in the tundish of a point before the molten steel Q _{td - out} (t) is the volume flow rate of the molten steel discharged from the turn-off at the previous point of time and C _{td -out} (t) is the molten steel concentration discharged from the turn- Dimensional relative density), and ρ _L is the density of the liquid molten steel.

In this case, the inlet volume flow rate Q _{td - in} of the subsequent molten steel in the turn-on time is calculated by the above-described formula (5), and the total weight W _td (t) , And the total gross weight (W _td (t +? T)) of the tinned steel at the present time is a value measured in real time at a predetermined time interval from the sensor provided at the time of turning, _{td - out (t + △ t} )) can be calculated as the sum of the casting speed and the mold cross-section size of the product measured by the sensors provided on one side of the strand, ρ _L is a liquid molten steel density 7000kg / m ³ to about 7400kg / m ³ , And more specifically about 7200 kg / m < ^{3 &} gt ;. (C _{td - in} (t)) of the subsequent molten steel flowing into the tundish at the time when the subsequent molten steel is supplied to the tundish and before it is mixed in order to supply the subsequent molten steel accommodated in the ladle to the tundish '1'. The initial value of the average non-dimensional relative concentration (C _{td - ave} (t)) of the molten steel in the previous turning point and the initial value of the non-dimensional relative concentration (C _{td - out} Is set to '0'.

The average non-dimensional relative concentration (C _{td - ave} (t +? T)) of the molten steel at the present time in turn is calculated based on the initial values set as described above.

Next, the value calculated by Equation (6) is applied to the average non-dimensional relative concentration (C _{td - ave} (t +? T)) of the molten steel in the turn- Dimensional non-dimensional relative concentration (C _{td - out} (t +? T)) of the nonlinear surface is calculated by the following equation (7).

When the mean non-dimensional relative concentration (C _{td - ave} (t + Δt)) of the molten steel in the turn-off time at the present time is calculated, the non-dimensional relative concentration (C _{td - out} (t +? t)) (S413). At this time, in the present invention, the dimensionless relative concentration (C _{td - out} (t +? T)) of the molten steel discharged from the tundish is calculated by using the following Equation (7).

C _{td - out} (t + Δt) is the non-dimensional relative concentration of molten steel discharged from the tundish at the present time, C _td _ _ave (t + Δt) _{td -in} (t +? t) is the non-dimensional relative concentration of molten steel flowing into the tundish at the present time. At this time, the average non-dimensional relative concentration (C _{td - out} (t +? T)) of the molten steel in the tundish is calculated and applied by Equation (6) as described above. The dimensionless relative concentration (C _{td - in} ) is 1. And f _td is the in-dash extrapolation factor, applying different extrapolation factors for the non-dimensional relative concentration of the strand center and the non-dimensional relative concentration of the surface of the strand. That is, within the extrapolation coefficient (f _{td _ center)} is 4 ± 2, within the extrapolation coefficient used for the calculation of the strand surface portion density (f _{td _ surface)} is 2.2 ± 0.6 is used for the calculation of the strand center concentration.

Next, using the dimensionless relative concentration (C _{td -out} (t +? T)) of the molten steel discharged from the tundish at the present time, the average non-dimensional relative concentration (C _{md -ave} ? T)) (S414), and in the present invention, it is calculated using Equation (8).

W _md (t) is a total of a molten steel in the mold at an earlier time, weight, C _{md - ave} (t) is the average dimensionless relative concentration of a molten steel in the mold at an earlier time, Q _{md - in} (t) is the mold in the previous point, the molten steel of the inlet volumetric flow rate, C _{md - in} (t) is the inlet concentration of a molten steel in a mold (dimensionless relative concentration), W _md at an earlier time (△ t + t) is a molten steel in a total weight of the mold at this time, Q _{md - out} (t) is the molten steel volumetric flow rate discharged from the mold, C _{md -} dimensionless relative density, ρ _L of the _out (t) is the steel grade (i.e., a strand) is discharged from the mold at an earlier time is a density of the liquid steel, 7000 a kg / m ³ to 7400 kg / m ^3, more specifically, for example, of about 7200kg / m ^3.

Here, the total weight of the molten steel in the mold at the present time (W _md (t + Δt)) and the total weight of molten steel in the mold at the previous time (W _md (t)) are calculated using the length and cross- . That is, it can be calculated through the formula of "total molten steel in the mold (Wmd) = (total length of the mold - length from the top of the mold to the meniscus) × cross sectional area of the mold × liquid molten steel density". Here, the cross-sectional area of the mold is equal to the cross-sectional area of the strand. Further, the flow rate of the strand (or steel type) discharged from the mold can be calculated as the sum of the product of the address speed measured by the sensor located at one side of the strand and the cross-sectional area of the mold. The non - dimensional relative concentration (C _{md - in} (t)) of the subsequent molten steel flowing into the mold at any previous point in time is always equal to the dimensionless relative concentration (C _{td - out} same. In addition, the average dimensionless relative concentration of a molten steel in the mold of the previous time _- initial value of a dimensionless relative concentration (Cmd-out (t)) of the molten steel discharged from the initial value and the mold of (C _{md ave} (t)) is zero '.

The average non-dimensional relative concentration (C _{md - ave} (t)) of the in-mold molten steel at the present time is calculated by the set initial values.

Next, the value calculated by the formula (8) is applied to the average dimensionless relative density (C _{md - ave} (t +? T)) of the molten steel in the mold at the present time, dimensionless relative concentration _{(C md - out (t +} △ t)) are the values calculated at the present time by the equation (9) to be described later is applied.

Thereafter, the dimensionless relative concentration C _{md - out} (t +? T) of the steel species (i.e., the strand) discharged from the mold at the present time is calculated (S415). In the present invention, the dimensionless relative concentration (C _{md - out} (t +? T)) of the steel species (that is, the strand) discharged from the mold at the present time is calculated by the following equation (9).

C _{md - out} (t + △ t) is a dimensionless relative concentration, C _md _ _ave (t + △ t) is the average dimensionless relative of a molten steel in the mold at the moment of the steel type (i.e., a strand) is discharged from the mold at the moment The concentration, C _{md - in} (t + Δt), is the dimensionless relative concentration of molten steel entering the mold at the present time. Here, the dimensionless relative concentration ( _{Cmd - out} (t +? T)) of the steel species discharged from the mold at the present time is the dimensionless relative concentration of the strand which is solidified and discharged or drawn out from the mold at present, Is a value to be calculated through the following equation. In addition, the average dimensionless relative concentration of a molten steel in the mold at the moment _{(C md _ ave (t +} △ t)) are applied, the value calculated by the above Equation 8, f _md is a within extrapolation coefficient, the strand center And a different internal extrapolation factor is applied to calculate the non-dimensional relative concentration of the surface portion and the non-dimensional relative concentration of the surface portion. That is, the internal extrapolation factor (f _{md _ center} ) used for calculating the non-dimensional relative concentration of the _center portion is 0.7 ± 0.4, the internal extrapolation coefficient (f _{md _ surface} ) used for calculating the non- Is 0.5 ± 0.2. In addition, the non-dimensional relative concentration of the molten steel flowing at this time in the mold _{(C md - in (t +} △ t)) are soon, dimensionless relative concentration of the molten steel discharged from the tundish at this time (C _{td - out} (t + (T)), the value calculated by the above-described Equation (7) is applied. In the case of molten steel discharged from the mold, the density value of the liquid molten steel is 7000 kg / m ³ to 7400 kg / m ³ , and more preferably about 7200 kg / m ³ , because the molten steel mainly consists of liquid molten steel.

Dimensional non-dimensional relative concentration of each of the center portion and the surface portion of the strand in real-time during the spinning operation in the above-described manner, In the casting direction) (S420).

For this purpose, a process of setting the position where the non-dimensional relative concentration acquisition of the surface portion of the strand starts and the position where the non-dimensional relative concentration acquisition of the center portion starts is performed in the longitudinal direction (or the casting direction) of the strand. This is because, as described above, in the continuous casting of two or more grades, the mixing portion between the previous steel species and the mixed steel species appears on the surface portion of the strand after the opening time of the succeeding ladle. In the case of the center portion, Mixing occurs. That is, the mixed and re-mixed molten steel produced through the tundish and the mold is diffused to the center of the non-solidified molten steel layer in the strand. Therefore, in the center portion of the strand, mixing occurs between the previous steel species and the succeeding steel species from the previous point of view compared with the surface portion, and the center portion is mixed at a position of -4 4 m from the strand position at the time of detection of the subsequent ladle opening signal .

Therefore, it is necessary to set the position where the concentration acquisition starts, in particular, the position where the center concentration acquisition starts.

Accordingly, in the present invention, the position of the strand at the time when the subsequent ladle opening signal is detected is set to the position where the dimensionless relative concentration measurement of the strand surface starts. Then, a position of -4 4 m at the strand position at the subsequent ladle opening time is set to a position where the dimensionless relative concentration acquisition of the strand center portion starts.

When the non-dimensional relative concentration starting position of each of the surface portion and the center portion of the strand is set, a strand position having a non-dimensional relative concentration of the calculated strand center portion and a non- (S420).

First, the position of the strand having the dimensionless relative density of the calculated surface portion is calculated by multiplying the mold discharge volume flow rate (Q _{md - out} ) and the liquid molten steel density in the strand by the area (A _md ) of the cross section of the strand and the solid phase density (? _s ), and the calculated length value can be obtained. This can be expressed by the following equation (10).

The reason why the solid-state density of the molten steel (7600 kg / m ³ to 8000 kg / m ³ ) is applied as the density value is that the longitudinal shrinkage due to the solidification of the liquid molten steel is considered.

The value calculated by Equation (10) is a length value, and the position of the point shifted by the calculated length value based on the meniscus position of the strand is the position of the strand having the surface portion density. The position of the strand having the calculated central concentration is the position of -4 ± 4 m from the position of the strand having the surface portion concentration obtained at the same time in the above.

As described above, in the present invention, the non-dimensional relative concentration of the central portion of the strand and the non-dimensional relative concentration of the surface portion are obtained in real time, and the longitudinal position of the strand having the non- . Then, the calculation time is counted from the time when the dimensionless relative concentration of each of the center portion and the surface portion of the strand is calculated, and is compared with the reference time in real time (S500).

On the other hand, in the continuous casting operation, the strand drawn out from the mold is conveyed in the casting direction, that is, the direction in which the cutter is located, according to the elapse of the casting time. Therefore, the mixed portion generated in the strand gradually approaches the scouring machine according to the elapsed operating time, and the mixing portion must be predicted before the mixed portion is positioned below the scraper. In other words, before the actual mixing part is located below the scavenging unit, the dimensionless relative concentration of the calculated center part reaches the first reference concentration, and the dimensionless relative concentration of the calculated surface part has to reach the second reference concentration. Therefore, in the embodiment of the present invention, the reference elapsed time is set in consideration of the casting speed of the gusset, and the reference time is counted from the starting point of calculation of the non-dimensional relative density of each of the center portion and the surface portion, , And reaches a predetermined position in front of the above-mentioned cutter. At this time, the predetermined position may be changed according to the position of the scraper, the operation equipment, or the operating conditions, and it is possible to estimate the time taken to reach the predetermined position from the casting speed at the time of normal lifting operation. This reference time can be obtained through the casting speed and varies according to the operating equipment or operating conditions as described above.

The acquisition time is counted in real time while acquiring the non-dimensional relative concentration of each of the center portion and the surface portion of the strand and compared with the reference time in real time (S500). If the acquisition time is within the reference time (yes) Dimensional relative concentration of the surface portion with the first reference concentration, and compares the non-dimensional relative concentration of the obtained surface portion with the second reference concentration (S600).

At this time, the position in the longitudinal direction of the strand in which the dimensionless relative concentration of the center reached the first reference concentration is set as the starting position of the mixing portion, the position in the longitudinal direction of the strand in which the dimensionless relative concentration of the surface portion reached the second reference concentration As the end position of the portion, the position from the start point to the end point of the mixing portion is predicted as the mixed portion position (S700). That is, when the non-dimensional relative concentration of the central portion reaches the first reference concentration, it repeats or ends the acquisition of the non-dimensional relative concentration at the central portion, and the position of the strand, I.e., the first cut position. When the dimensionless relative concentration of the surface portion reaches the second reference concentration, the non-dimensional relative concentration acquisition of the surface portion is repeated or terminated, and the position of the strand where the dimensionless relative concentration of the surface portion reaches the second reference concentration, End position, that is, the second cut-out position. Thereafter, the scraper cuts the first cut position and the second cut position, respectively, and cuts the mixed portion predicted from the strands (S1100).

On the contrary, if the dimensionless relative concentration of the center does not reach the first reference concentration or if the dimensionless relative concentration of the surface portion does not reach the second reference concentration, acquisition of the dimensionless relative concentration of each of the center portion and the surface portion of the strand (S410) And the position calculation step S420 of the dimensionless relative density are repeated. In addition, for example, when the dimensionless relative concentration of the center reaches the first reference concentration but the dimensionless relative concentration of the surface portion does not reach the second reference concentration, the acquisition of the dimensionless relative concentration at the center portion is repeated or terminated, Dimensional non-dimensional relative concentration acquisition and position calculation of the surface portion. On the other hand, when the dimensionless relative concentration of the surface portion reaches the second reference concentration but the dimensionless relative concentration of the center portion does not reach the first reference concentration, the acquisition of the dimensionless relative concentration of the surface portion repeats or ends, Dimensional relative concentration acquisition and position calculation process again.

As another example, the acquiring time is counted in real time while acquiring the non-dimensional relative concentration of each of the center portion and the surface portion of the strand, and the acquired time is compared with the reference time in real time (S500) NO), the non-dimensional concentration acquisition of each of the central portion and the surface portion of the strand is terminated (S800). In operation S900, it is determined whether the combination of the previous steel type and the subsequent steel type currently being operated is included in the pre-set mixed-section length table.

For example, in a case where the combination of the gypsum currently in operation is a kind included in the pre-set mixing section trimming length table, the strand is truncated to the trimming length in the mixing section trimming length table (S1200). At this time, the cutting length can be cut to the cut length based on the meniscus position of the strand. However, if the combination of bimanals currently being operated is of a type not found in the pre-set mixing section length table, the maximum length is truncated based on the meniscus position of the strand (S1300).

Referring to FIGS. 13 and 14, it can be seen that the position or truncation position of the mixing portion calculated by the method according to the embodiment of the present invention and the position or truncation position of the mixing portion detected by direct component measurement of the strands are identical. 14, when the dimensionless relative density of the center portion reaches the first reference density and the dimensionless relative density of the surface portion reaches the second reference density, the non-dimensional relative concentration acquisition and position calculation of the surface portion are automatically performed And terminates.

In the above description, a method of predicting the mixing portion by acquiring the center portion and the surface non-dimensional concentration in the height direction of the strand has been described. However, the non-dimensional concentration acquisition position is not limited to the center and surface non-dimensional concentration, and the non-dimensional concentration can be obtained at a plurality of positions in the height direction of the strands or at different positions of the strands to predict the mixing portion.

Hereinafter, the continuous casting method according to an embodiment of the present invention will be sequentially described with reference to FIGS. 1 to 7 and 12. At this time, the steel types that have relatively earlier casting operations are referred to as the previous steel types, and the ones where the casting operation is started as the succeeding steel types. The contents overlapping with those described above will be omitted or briefly explained.

First, the peripheral speed is lowered at the end of the operation of the previous steel grade, and when the remaining amount of the previous steel grade of the tundish is less than a predetermined amount, the PLC (Programmable Logic System) transmits the open pile virtual signal at step S200. Then, the turn-off weight is measured in units of milliseconds (ms), for example, in units of 200 ms from the point at which the virtual pager signal of the subsequent ladle is transmitted (S220). Subsequently, an average value of turn-off weights is calculated at a constant interval of seconds (s), for example, 1 second or 2 seconds, in turn, measured in milliseconds (S230), and the calculated average turn The weight of the dice is analyzed in real time and it is determined whether the weight is continuously increased (S240). That is, when both W _td (t) -W _td (t-? T) and W _td (t) -W _td (t- 2 *? T) t is determined as the opening time of the subsequent ladle, and the subsequent ladle opening signal is detected (S200).

After the open pseudo virtual signal is transmitted (S210), data for prediction of the strand mixing part is stored in the control unit of the continuous casting facility (S100). That is, the amount of molten steel remaining in the tundish, the casting speed, the component concentration of the molten steel of the steel product currently being operated (hereinafter referred to as the previous steel product), and the component concentration of the molten steel . At this time, the amount of the turn-off remaining amount and the casting speed are stored from the time point of t-4 * DELTA t so that the mixing part can be predicted in real time. Further, in the case of a continuous casting facility in which a plurality of strands are generated, it is determined whether or not each strand is operated, and the casting speed in each strand is stored.

Next, the first reference concentration and the second reference concentration for predicting the gaseous mixture portion of the strand to be solidified in the mold are set using the component concentration data of the previous steel species and the component concentration data of the subsequent steel species stored in the above (S300). More specifically, among the upper limit non-dimensional concentration values for each component of the previous steel species, the lowest non-dimensional concentration value is set as the first reference concentration. Further, among the lower limit non-dimensional concentration values for each component of the succeeding steel species, the highest non-dimensional concentration value is set as the second reference concentration. In the case of the non-dimensional concentration calculation for each component concentration, when the lower non-dimensional concentration of the previous steel grade is larger than the upper non-dimensional concentration of the previous steel grade, the lower non-dimensional concentration value of the previous steel grade is the upper non- The upper limit non-dimensional concentration value of the previous steel type is replaced with the lower limit non-dimensional concentration value of the previous steel type. In addition, when the lower limit non-dimensional concentration of the succeeding grade is larger than the upper limit non-dimensional concentration of the subsequent grade, the lower limit non-dimensional concentration value of the subsequent grade is the upper limit non-dimensional concentration value of the subsequent grade, The concentration value is replaced by the lower limit non-dimensional concentration value of the subsequent steel grade. This is applied when the component concentration of the previous steel grade is higher than that of the subsequent steel grade.

The first reference concentration and the second reference concentration are reference values for predicting the mixing portion and are changed depending on the types and combinations of the previous and subsequent steel species.

When the first reference concentration and the second reference concentration for mixing part prediction are set, the non-dimensional relative concentration of each of the central portion and the surface portion of the strand is measured in real time from the time point of detection of the subsequent ladle opening signal, And the non-dimensional relative concentration calculation time is counted from the time point (t-2 *? T) at which the subsequent ladle opening signal is detected (S410). Further, the position of the strand at the time when the subsequent ladle-opening signal is transmitted is set to the position where measurement of dimensionless relative density of the strand surface portion is started. Then, a position of -4 4 m at the strand position at the subsequent ladle opening time is set to a position where the dimensionless relative concentration acquisition of the strand center portion starts.

The method for acquiring the dimensionless relative concentration of the center portion and the surface portion is as follows. Step S411 of calculating the following molten steel inflow volume flow rate Q _{td - in in} turn by using Equation (5) tundish in subsequent molten steel inlet volumetric flow _{rate-calculating} the (Q _{td in)} a tundish molten steel average dimensionless relative concentration _{(C ave (t + △ t} )) of the at this point in time by applying equation 6 (S412 ), the average dimensionless relative concentration (C _ave) a dimensionless relative concentration _{(C td-out (t +} △ of molten steel to be applied to equation (7) discharged from the tundish at this point in the tundish the molten steel calculated from the present time t)) step (S413), the non-dimensional relative concentration (C _td of the molten steel discharged from the tundish calculated at this time to calculate a _- by applying the _out (t + △ t)) in equation (8) the mold at the moment (S400) of calculating the average non-dimensional relative concentration ( _{Cmd - ave} (t +? T)) of the molten steel The relative non-dimensional relative concentration (C _{td - out} (t +? T)) of the molten steel discharged from the dies and the average non-dimensional relative concentration (C _{md - ave} applied to 9, and a step (S415) for calculating a dimensionless relative concentration (C _{-out md} (t + △ t)) of the strand is discharged from the mold at this time. At this time, the non-dimensional relative concentration of the molten steel flowing at this time in the mold in Equation _{8 (C md - in (t} + △ t)) is a dimensionless relative concentration of the molten steel discharged from the tundish at this time (C _{td -} flowing a _{- (out (t + △ t} C td)) with a mold of equation _{8 out (t + △ t)} ) , so, the non-dimensional relative concentration of the molten steel discharged from the tundish at this time calculated by the equation (7) This is applied to the dimensionless relative concentration (C _{md - in} (t + Δt)) of molten steel.

(7) for calculating the dimensionless relative concentration (C _{td - out} (t +? T)) of the molten steel discharged from the present tundish in the concentration calculation method described above, By applying the coefficient of internal extrapolation for calculating the surface portion to the inner extrapolation factor (f) in each of the equations (9) to (9) for calculating the dimensionless relative concentration ( _{Cmd - out} The concentration can be calculated. That is, 2.2 ± 0.6 is applied to the internal extrapolation factor (f) in the equation (7) to calculate the dimensionless relative concentration (C _{td - out} (t + Δt)) of the molten steel discharged from the tundish, (0.5) is applied to the inner extrapolation factor (f) in the equation (9) to calculate the dimensionless relative concentration (C _{md - out} (t +? T) can do. Similarly, the internal extrapolation in equation (7) to calculate the dimensionless relative concentration (C _{td - out} (t +? T)) of molten steel discharged from the tundish at the present time to obtain the dimensionless relative concentration of the strand center, In order to calculate the dimensionless relative concentration (C _{md -out} (t +? T)) of the steel grade discharged from the mold at the present time by applying 4? 2 to the coefficient (f) ), It is possible to obtain the dimensionless relative concentration of the strand center portion.

When the non-dimensional relative concentration of each of the strand, the center portion, and the surface portion is obtained in real time as described above, the position in the strand length direction having the non-dimensional relative concentration of the calculated center portion and the non-dimensional relative concentration of the surface portion is calculated (S420). The position of the strand having the dimensionless relative density of the calculated surface portion can be obtained by multiplying the product of the mold discharge volume flow rate Q _{md - out} and the liquid molten steel density in the strand by the area A _md of the cross section of the strand, And the solid phase density (ρ _s ) of molten steel. The density value of a 7600 kg / m ³ solid phase density of the molten steel to about 8000 kg / m ^3, more preferably apply about 7800kg / m ^3. The position of the strand having the non-dimensional relative concentration of the obtained central portion is -4 ± 4 m from the position of the strand having the dimensionless relative density of the surface portion calculated at the same time in the above.

Dimensional non-dimensional relative concentration of each of the center portion and the surface portion of the strand in real time, and while calculating the longitudinal position of the strand having the non-dimensional relative concentration of each of the obtained central portion and surface portion, The reference time is compared with the reference time in real time (S500). If the calculated time is within the reference time (yes), the non-dimensional relative concentration of each of the calculated central portion and the surface portion of the strand is compared with the first and second reference concentrations (S600).

When the non-dimensional relative concentration of the central portion obtained in real time reaches the first reference concentration and the dimensionless relative concentration of the surface portion reaches the second reference concentration, the concentration calculation is ended and the mixing portion is predicted (S700). That is, when the non-dimensional relative concentration of the center portion obtained in real time reaches the first reference concentration, the calculation of the longitudinal position of the strand having the non-dimensional relative concentration of the center portion is terminated, The strand position of the concentration is set to the start position of the mixing section. When the non-dimensional relative concentration of the surface portion obtained in real time reaches the second reference concentration, the longitudinal position calculation of the strand having the dimensionless relative concentration of the surface portion is terminated, and the dimensionless relative The strand position of the concentration is set to the end position of the mixing section. Here, the region where the dimensionless relative concentration of the obtained center portion has the first reference concentration value and the point of the strand having the dimensionless relative concentration of the obtained surface portion having the second reference concentration value are predicted as the mixing portion . Thereafter, the slicing machine automatically cuts off the starting point and the ending point of the mixing part, thereby cutting off the gaseous mixed part from the strand (S1100).

On the other hand, if the dimensionless relative concentration of the center portion does not reach the first reference concentration, or if the dimensionless relative concentration of the surface portion does not reach the second reference concentration, acquisition of the dimensionless relative concentration of the center portion and the surface portion of the strand (S410) Dimensional non-dimensional relative concentration (S420) is repeated.

If the concentration acquisition and position calculation time exceeds the reference time (NO), the central portion and surface portion concentration acquisition and position calculation of the strand are terminated (S800). In operation S900, it is determined whether the combination of the previous steel type and the succeeding steel type in operation is a combination in the preset mixed steel cut length table. For example, in the case where the combination of the gypsum currently in operation is a combination in the pre-set mixing section trimming length table, the strand is truncated to the trimming length in the mixing section trimming length table (S1200). At this time, the cutting length can be cut to the cut length based on the meniscus position of the strand. However, if the combination of the currently working bifurcations is of a type that does not exist in the pre-set blending section length table, the cutting is performed to a predetermined length of cut, for example, a maximum length based on the meniscus position of the strand (S1300). After the constant length cutting, the casting before and after the mixing part is set as an abnormal part, and the component is analyzed by the component analyzer.

FIG. 15 is a graph illustrating a length of a mixing part for one year through a mixing part prediction method according to an embodiment of the present invention.

Referring to FIG. 15, it can be seen that the length of the mixing portion varies from 0 to 23 m according to the real-time operation method and the concentration of the steel species. That is, according to the present invention, the length and position of the mixing portion are calculated at each time of operation of the boats, without cutting the boats to a certain length irrespective of the operating conditions, and the accuracy of the mixing portion is improved by improving the accuracy . More specifically, the non-dimensional relative concentration of each of the center portion and the surface portion of the strand is obtained in real time, and the length and position of the mixing portion are derived using the real-time relative density. Therefore, it is possible to prevent profitability deterioration due to excessive cutting of the mixing part through the present invention, and it is possible to prevent the problem of shipping the defective product to the customer company due to undercutting of the mixing part.

110, 120: Ladder 200: Turn Dish
300: mold 400:

Claims (25)

As a continuous casting method of this kind,
Acquiring, in real time, non-dimensional relative concentrations of succeeding steels for the previous steel species in the inside and the surface portion of the strand to be continuously cast;
Calculating a position in a longitudinal direction of a strand having a non-dimensional relative density of an inner surface portion and a surface portion obtained in real time;
Comparing the acquired relative intensities of the inner and the outer dimensions with the reference concentration to predict the mixing portion in the strand; And
Cutting the predicted mixing portion; Of the continuous casting method. The method according to claim 1,
Wherein the position of the strand for obtaining the dimensionless relative density is the center portion and the surface portion in the height direction of the strand. As a continuous casting method of this kind,
Using the relative amounts of the previous and subsequent steels in the tundish and the relative amounts of the previous and succeeding steels in the mold, Dimensional relative density of the subsequent steel species in real time;
Calculating a position in the longitudinal direction of the strand having the dimensionless relative density obtained in real time;
Comparing the dimensionless relative concentrations with the reference concentration to predict a mixing part in the strand; And
Cutting the predicted mixing portion; Of the continuous casting method. The method of claim 3,
Wherein the plurality of positions in the height direction of the strand for obtaining the dimensionless relative density include the central portion and the surface portion of the strand. The method according to claim 1 or 3,
And setting the reference concentration before the step of acquiring the dimensionless relative concentration of the subsequent steel species for the previous steel species in the continuously cast strand in real time,
The step of setting the reference concentration comprises:
Setting a lowest concentration among the upper limits for each of the components of the previous steel type to a first reference concentration;
Setting the highest concentration among the lower limit concentrations for the respective components of the subsequent steel species to a second reference concentration;
Of the continuous casting method. The method of claim 5,
In the step of setting the first reference concentration and the second reference concentration,
Calculating a component concentration of the previous steel product as a lower limit non-dimensional concentration and an upper non-dimensional concentration;
Setting a lowest non-dimensional concentration among the upper non-dimensional concentrations for the respective components of the previous steel type as a first reference concentration;
Calculating a component concentration of the subsequent steel product as a lower limit non-dimensional concentration and an upper non-dimensional concentration;
Setting a best non-dimensional concentration as a second reference concentration among the lower-limit non-dimensional concentrations for the components of the succeeding steel species;
Of the continuous casting method. The method of claim 6,
In calculating the concentration of each component of the previous steel product as the lower limit non-dimensional concentration and the upper limit non-dimensional concentration,
When the lower non-dimensional concentration of the previous steel grade is larger than the upper non-dimensional concentration of the previous steel grade, the lower non-dimensional concentration value of the previous steel grade is replaced with the upper non- dimensional concentration value of the previous steel grade, A process of substituting the lower limit non-dimensional concentration value of the previous steel grade;
/ RTI >
In calculating the concentration of each component of the subsequent steel type as the lower limit non-dimensional concentration and the upper limit non-dimensional concentration,
When the lower limit non-dimensional concentration of the succeeding steel species is larger than the upper non-dimensional concentration of the subsequent steel product, the lower limit non-dimensional concentration value of the subsequent steel product is replaced with the upper non-dimensional concentration value of the subsequent steel product, A process of substituting the lower limit non-dimensional concentration of the steel species;
Of the continuous casting method. The method according to claim 2 or 4,
Dimensional non-dimensional relative concentration of the center portion and the non-dimensional relative concentration of the surface portion obtained is determined as a mixed state when the non-dimensional relative concentration deviates from the reference concentration,
And determining a position in the longitudinal direction of the strand having a dimensionless relative density at which at least one non-dimensional relative concentration of at least one of the obtained central portion and the non-dimensional relative concentration of the surface portion deviates from the reference concentration as a mixing portion. The method of claim 8,
Determining a position in the longitudinal direction of the strand where the non-dimensional relative concentration of the obtained central portion reaches the reference concentration as the starting point of the mixing portion,
And determining the position in the longitudinal direction of the strand in which the dimensionless relative concentration of the obtained surface portion reaches the reference concentration as the end point of the mixing portion. The method according to claim 2 or 4,
Before the process of acquiring the dimensionless relative concentration of the subsequent steel species for the previous steel species,
A process of receiving and storing the concentration data of each of the molten steel remaining in the tundish, the casting speed, the previous steel grade and the succeeding steel grade, online; And
Detecting a pore signal of a subsequent ladle;
Of the continuous casting method. The method of claim 10,
Dimensional relative density of each of the center portion and the surface portion of the strand from the time point at which the opening signal of the subsequent ladle is detected,
Counting a non-dimensional concentration acquisition time from a time point at which the opening signal of the subsequent lugs is detected, and comparing the non-dimensional concentration acquisition time with a reference time in real time;
Comparing the dimensionless relative concentration of the obtained center portion with a first reference concentration when the dimensionless concentration acquisition time is less than or equal to a reference time and comparing the dimensionless relative concentration of the obtained surface portion with a second reference concentration;
Terminating the acquisition of the dimensionless relative concentration of each of the central portion and the surface portion of the strand when the concentration acquisition time exceeds the reference time;
Of the continuous casting method. The method of claim 11,
After completing the acquisition of the dimensionless relative concentration of each of the center portion and the surface portion of the strand,
Determining whether the type of the previous steel type and the subsequent steel type are included in the predefined gypsum cut-off table;
If the type of the previous steel type and the succeeding steel type that are currently in operation are included in the pre-set pre-cut table, the process is truncated to the cut length of the pre-selected grade.
A step of cutting to a predetermined cut length when the kind between the previous steel type currently being operated and the subsequent steel type is not included in the predetermined cut-off type table;
Of the continuous casting method. The method of claim 10,
In the process of detecting the next ladle opening signal,
Transmitting a virtual ladle opening signal;
Detecting the weight of the turn-by-turn in real time in milliseconds (ms) from the time when the virtual ladle-opening signal is transmitted;
Calculating a weight of the turn-disc detected in units of milliseconds (ms) at an average turn-off weight of a predetermined time interval in seconds; And
Setting a subsequent ladle opening timing at a time point when the average turn-off weight continuously increases;
Of the continuous casting method. 14. The method of claim 13,
W _td (t) is the weight of the remaining tundish at the current point, and W _td (t-? T) is the weight of the tundish at the previous point,
The _{W td (t-2 * △} t) when both equal to or greater than '0', t-2 * △ t - W td (t) - W td (t- △ t) and, W _td (t) It is determined that the opening time of the subsequent ladies is determined,
Dimensional non-dimensional relative concentration of each of the central portion and the surface portion of the strand from the time t-2 *? T,
t-4 * Continuous casting method of the bimetallic type which stores the amount of turn-around and the casting speed from the point of time t. The method according to claim 2 or 4,
The process of acquiring the dimensionless relative concentration of the subsequent steel species for the previous steel species at the center portion and the surface portion of the strand,
Calculating an inlet volume flow rate (Q _{td - in} ) of the subsequent molten steel in the tundish;
Calculating a mean non-dimensional relative concentration (C _{td - ave} (t +? T)) of the molten steel during turning at the present time using the inlet volume flow rate (Q _{td - in} ) of the subsequent molten steel in the turn-off time;
Tundish molten steel average dimensionless relative concentration of the present time _- by using the _{(C td ave (t + △} t)), non-dimensional relative concentration of the molten steel discharged from the tundish at this time (C _td-out (t + ? T));
The current non-dimensional relative concentration of the molten steel discharged from the tundish point _- using the _{(C td out (t + △} t)), the average dimensionless relative concentration of a molten steel in the mold at the moment (C _md-ave (t + △ t));
( _{Cmd - ave} (t +? T)) of the present molten steel in the mold and the dimensionless concentration ( _{Cmd - in} (t +? T) of molten steel flowing into the mold at the present time the step of calculating a dimensionless relative concentration _{(C md _ out (t +} △ t)) of the strand is discharged from the mold at the moment;
Of the continuous casting method. 16. The method of claim 15,
The inlet volume flow rate Q _{td - in} of the subsequent molten steel in the turn-off time is calculated by the equation (5)
&Quot; (5) "

(W _td (t) is a tundish molten steel shot weight, W _td (t + △ of the earlier time t) is a tundish molten steel total weight of this time, Q _{td - out} the molten steel volumetric flow rate discharged from the tundish, ρ _L is the density of the liquid molten steel)

(C _{td - ave} (t +? T)) at the present time is calculated by the equation (6)
&Quot; (6) "

(C _{td _ ave} (t) is the average dimensionless relative concentration of the tundish the molten steel in the earlier time, Q _{td - in} (t) is the inlet volume flow rate of the molten steel flowing into the tundish at an earlier time, C _{td - in} ( t) is the inlet concentration of the follow-up molten steel tundish of an earlier time (dimensionless relative concentration), Q _{td - out} (t) is the molten steel volumetric flow rate discharged from the tundish of an earlier time, C _{td - out} (t) is the previous The molten steel concentration (non-dimensional relative concentration) discharged from the turn-around of the time point, and ρ _L is the density of the molten steel in liquid phase)

The molten steel concentration (C _{td - out} (t +? T)) discharged from the tundish at the present time is calculated by the equation (7);
&Quot; (7) "

(f _td is the turn-dish within extrapolation _{coefficient, C td _ ave (t +} △ t) is the average dimensionless relative concentration of a molten steel in the tundish at this _{point, C td - in (t +} △ t) is in the tundish at the present time Dimensionless relative concentration of molten steel entering)

At this point in time, the average molten steel concentration in the mold (C _{md - ave} (t +? T)) is calculated by Equation (8)
&Quot; (8) "

(W _md (t) is a molten steel in the mold shot at an earlier time, weight, C _{md - ave} (t) is the average dimensionless relative concentration of a molten steel in the mold at an earlier time, Q _{md - in} (t) is the mold in the previous point, inlet volumetric flow rate of the molten steel, C _{md - in} (t) is the inlet concentration of a molten steel in the mold at an earlier time (dimensionless relative _{concentration), W md (t + △} t) is a molten steel in a total weight of the mold at this time, Q _{md - out} (t) is the volumetric flow rate of molten steel discharged from the mold, C _{md - out} (t) is the dimensionless relative density of the strand discharged from the mold at the previous point of time, and ρ _L is the density of the molten steel)

Density of the strand is discharged from the mold at the present time _{(md _} C _out (t + △ t)) is calculated by the equation (9)
&Quot; (9) "

(f _md is molded within the extrapolation _{coefficient, C md _ ave (t +} △ t) is the average dimensionless relative concentration, C _md of a molten steel in the mold at this time _- that is introduced into the mold at the present time _in (t + △ t) steel Dimensional non-dimensional relative concentration)
Continuous casting method of cast steel. 18. The method of claim 16,
In the process of calculating the dimensionless relative density of the strand center portion,
4 < RTI ID = 0.0 > + 2 < / RTI > is applied to the inner extrapolation coefficient (f _td )
(C _{md - out - center} ) of the strand center by applying 0.7 ± 0.4 to the inner extrapolation factor (f _md ) of Equation (9). 18. The method of claim 16,
In calculating the dimensionless relative density of the surface portion of the strand,
The internal extrapolation coefficient (f _td ) of Equation (7) is 2.2 ± 0.6,
(C _{md - out - surface} ) of the surface portion of the strand by applying 0.5 ± 0.2 to the internal extrapolation factor (f _md ) of Equation (9). 18. The method of claim 16,
Continuous casting method of yigangjong applying the equation (5), 6, using the liquid density in the molten steel density (ρ _L) value at 8, respectively, and to the molten steel density of 7000 to 7400 kg / m ³ value. The method of claim 10,
Setting a position of the strand at which acquisition of dimensionless relative concentration of the strand surface portion starts; And
Setting a position of the strand at which acquisition of dimensionless relative concentration of the strand center portion starts;
/ RTI >
Setting a strand position at the subsequent ladle opening time to a position at which a dimensionless relative concentration acquisition of the strand surface portion starts,
And setting a position of -4 4 m at the strand position at the subsequent ladle opening time to a position at which the dimensionless relative concentration acquisition of the strand center portion starts. The method of claim 20,
In the process of calculating the longitudinal position of the strand having the dimensionless relative density of the obtained surface portion,
The continuous casting of the gypsum obtained by dividing the molten steel volume flow rate (Q _{md - out} ) discharged from the mold by a value obtained by dividing the area (A _md ) of the cross section of the strand by the solid phase density (ρ _s ) Way.

&Quot; (10) "

(Q _{md _ out} is the volume flow rate of the molten steel discharged from the mold, A _md is the cross-sectional area of the strand, and ρ _s is the solid-phase molten steel density of 7600 to 8000 kg / m ³ ) 23. The method of claim 21,
In the process of calculating the longitudinal position of the strand having the dimensionless relative density of the obtained center portion,
And setting a position of -4 4 m at a position having a dimensionless relative density of the obtained surface portion to a position having a dimensionless relative density of the center portion. 23. The method of claim 22,
Dimensional non-dimensional relative concentration of the strand surface portion obtained in real time from the point of the strand where the non-dimensional relative concentration of the strand center portion obtained in the real time reaches the first reference concentration is mixed to the point of the strand where the non- A continuous casting method of the brass type foreseeing the brass part. 23. The method of claim 22,
Setting a position of the strand at which the dimensionless concentration of the strand center obtained in the real time reaches the first reference concentration to the first cutout position;
Setting a position of the strand in which the dimensionless concentration of the strand surface portion obtained in real time reaches the second reference concentration to a second cut position of the strand;
Performing trimming at each of the first cut position and the second cut position to cut the mixed portion;
Of the continuous casting method. The method according to claim 1 or 3,
Wherein the process of predicting the mixing portion of the strand and the cutting process of the predicted mixing portion are performed in an online process.

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